A large area just east of the Catoctin Mountain range in Loudoun County is comprised of limestone and “Karst terrain” areas. Karst terrain is characteristic of regions that are underlain by limestone and dolomite bedrock. The limestone geology of carbonate deposits in Karst terrain areas is dissolved over time by mildly acidic precipitation, creating fissures. The deposits are highly permeable, allowing surface water to pass through quickly to underlying aquifers and eating away at the limestone. The terrain is also characterized by the presence of certain natural features, such as sinkholes and rock outcrops. In this outcrop area, cavities along vertical joints and sinkholes provide a direct link between the land surface and the water table. Precipitation on the outcrop area tends to infiltrate rapidly into the ground, recharging ground water. However, this land does not have natural protections of the underlying groundwater and just as the cavities are major avenues for ground-water recharge, they also are major route for contaminants to enter and spread throughout the groundwater. Experience in Florida and Texas has shown that Karst terrain is susceptible to subsidence and the creation of sinkholes as well as the easy an wide spread contamination of groundwater. Development on Karst terrain must be carefully managed to protect the property owners.
Uncontrolled development on limestone could result in contamination of groundwater and the drinking water wells that tap into it and significant subsidence and the creation of sink holes that could result in the ruination of property. Loudoun County is attempting to pass amendments to the zoning ordinances that would create a Limestone Overlay District (LOD). There are citizens of the proposed district who are up in arms against this, but also people who support this. The key component of this ordinance is control of future development. The proposed ordinance provides that no preliminary plan of subdivision shall be approved where a well and/or sewage disposal system is to be provided for each building lot in the subdivision, until written approval of proposed locations for such systems has been secured from the Health Director. This is to ensure that the groundwater supply is capable of supporting needs of the eventual inhabitants of the subdivision and the land can support the septic needs of the development without impacting the water supplies of existing residents and creating sinkholes that could endanger their properties. The goal is to make sure we only build what the land can support, that we accept the limits of the earth.
I believe strongly that Loudoun County should control development and abuse of the environment. However, it is essential that the method of control does not turn into a blunt instrument for stopping growth and creating excessive burdens on existing homeowners. Loudoun’s proposed ordinance must contain a time limit for response (or risk turning Virginia into California) say 90 or 120 days. Within that time limit for response, Loudoun must make a decision or the project is presumed to be approved. If the project is rejected, then the county must identify the reasons for the rejection in writing. In addition to the restrictions on new developments is a series of restrictions on existing homeowners that many feel are overly burdensome or misdirected. Loudoun County is actually surprised that homeowners are up in arms at the series of limitations that Loudoun proposes putting on their properties modeled on the Chesapeake Bay Protection Act.
Loudoun County should consider allowing all modifications to existing structures provided that such alteration does not encroach into a Karst/Sensitive Environmental Feature Setback. Limitations on the size of outbuildings (sheds) are not critical to the protection of the overall area. Loudoun County should loosen up on the restrictions to the existing homeowners, however, they should require all homeowners in the area to have their septic systems whether traditional or alternative inspected annually for potential failures and the tanks pumped every three years. Those steps would more directly protect the groundwater from contamination and allow existing homeowners peaceful enjoyment of their property.